Studies encompass the physiology, behavior, genetics, and vector competence of mosquito vectors of malaria with particular emphasis on members of the genus Anopheles and factors which mediate the development of the malaria parasite in these insects. a) Techniques have been developed for infecting mosquitoes with in vitro fertilized zygotes of malaria parasites to determine conditions necessary for establishment of the parasite of the mosquito gut. b) Attempts are underway to quantify the effects of malarial infection on the longevity of mosquito vectors. c) Genetic and physiologic factors which determine the susceptibility of mosquitoes to infection are being examined in several important vector species. Chemical mutagens are being used to induce genetic changes which could render a vector species refractory to the malaria parasite and therefore unable to transmit the disease.